1. Field of the Invention
The present invention relates to piezoelectric components, and in particular, to a piezoelectric component such as a trap filter for eliminating signal having a specific frequency and a discriminator for discriminating a signal.
2. Description of the Related Art
A Piezoelectric component, such as a trap filter and a discriminator utilizing thickness shear vibration and thickness longitudinal vibration, generally has a structure including a rectangular piezoelectric substrate having vibrating electrodes provided on both surfaces thereof, a case made of alumina for accommodating the piezoelectric substrate, and a lid member for closing the case having the piezoelectric substrate therein. The piezoelectric substrate is supported in the case such that the vibrating portion thereof can freely vibrate. In the piezoelectric component having this structure, since thickness shear vibration occurs in a vibrating mode having a nodal point at the center of the thickness of the piezoelectric substrate, damping members of silicone rubber are respectively applied to the surfaces of the piezoelectric substrate with vibrating electrodes provided thereon so that electrical characteristics such as attenuation, group delay characteristics, and distortion rate are adjusted to have desired values.
Furthermore, in the conventional piezoelectric component, damping members are respectively applied to both surfaces of the piezoelectric substrate, so that application of the damping member has to be performed twice to the piezoelectric substrate. Therefore, the number of manufacturing processes of the piezoelectric component is increased. This results in a problem of increased manufacturing costs of the piezoelectric component.
To overcome the problems described above, preferred embodiments of the present invention provide a low-cost piezoelectric component having a structure and arrangement that simplifies manufacture and achieves excellent electrical characteristics.
A preferred embodiment of the present invention provides a piezoelectric component including a piezoelectric element having a piezoelectric substrate with vibrating electrodes provided on both surfaces thereof, the piezoelectric element vibrating in a thickness shear mode, and a damping member having a predetermined hardness disposed on one of the surfaces of the piezoelectric substrate so as to cover the vibrating electrode provided thereon.
Due to the structure of the above-described piezoelectric component, desired electrical characteristics are achieved by arranging the damping member having an appropriate hardness on only one surface of the piezoelectric substrate. More specifically, when a damping member having a Shore hardness of about 35 to about 80 is used, attenuation characteristics and group delay characteristics satisfying the required standard for a trap filter can be achieved by arranging the damping member on only one surface of the piezoelectric substrate.
Furthermore, when the damping member having a Shore hardness of about 80 to about 100 is used, distortion rate characteristics satisfying the required standard for a discriminator can be achieved by arranging the damping member on only one surface of the piezoelectric substrate.
Other features, elements, characteristics and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention which refers to the accompanying drawings.